Horror Film The Exorcist Had A Real Life Murderer In It

And if you didn't think that anything could make William Friedkin's 1973 classic more terrifying than it already is, guess what, you really, really can.

Arguably one of the most chilling scenes in the film, the clip sees Regan, the 12-year-old girl possessed by the occult, taken to hospital to undergo tests, during which a catheter is inserted into her neck through an artery, and in response, the girl grimaces as blood spurts from her neck.

But this is where it gets very creepy, because one of the hospital technicians in that sequence was Bateson, who was convicted in 1979 for the murder of film journalist Addison Verrill.

He was also suspected of a number of murders within the gay community of Manhattan, New York, in the 70s.

Bateson's story has been revisited countless times over the years, most recently because he was one of the serial killers featured in the acclaimed Netflix crime drama Mindhunter.

He came to the attention of Friedkin when the director visited the New York University Medical Centre, where Bateson worked, to undertake some research. Impressed by his work, Friedkin invited Bateson to work as an extra on The Exorcist, and it is his character who calmly explains to Regan what will happen to her during the procedure.

Unfortunately what happened to Bateson after the film becomes a very dark tale indeed.

Although ultimately convicted for his 1979 murder of Verrill, Manhattan police had been suspicious of Bateson for some time following the deaths of several gay men.

Verrill himself was found beaten and stabbed to death in his own flat, after which the journalist's friend - fellow writer Arthur Bell - urged the killer to come forward via a piece in US news weekly The Village Voice.

Bell himself was instead contacted over the telephone by someone taking responsibility for the death.

After going out partying together and subsequently ending up back at Verrill's flat, the caller supposedly became enraged when his advances were rejected.

"I needed money and I hated the rejection. I decided to do something I'd never done before," he had told Bell. Allegedly hitting Verrill with a frying pan, he then stabbed the writer when he was knocked out, before stealing some cash, a credit card, Verrill's passport and some clothes.

The caller claimed he wanted to 'atone' for other crimes, but the next call Bell received came from a man going under the name 'Mitch' - who promptly accused Bateson of the murder. The fleeting movie actor was ultimately sentenced to 20 years in jail for the Verrill murder, although none of the others stuck - despite Bateson allegedly confessing to his friend Richard Ryan.

Released in 2003 after being granted parole, nothing is known of Bateson after this time - although a social security record shows a Patrick F. Bateson with the same birthdate passing away in 2012, with the murders of the other men in 1970s Manhattan still no nearer to being solved.